CA1331620C - Process for the production of 2-thiocyanomethylthiobenzothiazole - Google Patents
Process for the production of 2-thiocyanomethylthiobenzothiazoleInfo
- Publication number
- CA1331620C CA1331620C CA000612630A CA612630A CA1331620C CA 1331620 C CA1331620 C CA 1331620C CA 000612630 A CA000612630 A CA 000612630A CA 612630 A CA612630 A CA 612630A CA 1331620 C CA1331620 C CA 1331620C
- Authority
- CA
- Canada
- Prior art keywords
- glycol
- ether
- solvent
- solution
- thiocyanate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D277/00—Heterocyclic compounds containing 1,3-thiazole or hydrogenated 1,3-thiazole rings
- C07D277/60—Heterocyclic compounds containing 1,3-thiazole or hydrogenated 1,3-thiazole rings condensed with carbocyclic rings or ring systems
- C07D277/62—Benzothiazoles
- C07D277/68—Benzothiazoles with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached in position 2
- C07D277/70—Sulfur atoms
- C07D277/74—Sulfur atoms substituted by carbon atoms
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Thiazole And Isothizaole Compounds (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
- Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
- Polymerisation Methods In General (AREA)
- Photoreceptors In Electrophotography (AREA)
- Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for the manufacture of 2-thiocyanomethylthiobenzo-thiazole. 2-Chloromethylthiobenzothiazole is reacted, in the presence of at least one glycol ether as a solvent for the reaction, with either an alkali metal or an ammonium thiocyanate at a temperature and for a time sufficient to produce the 2-thio-cyanomethylthiobenzothiazole.
A process for the manufacture of 2-thiocyanomethylthiobenzo-thiazole. 2-Chloromethylthiobenzothiazole is reacted, in the presence of at least one glycol ether as a solvent for the reaction, with either an alkali metal or an ammonium thiocyanate at a temperature and for a time sufficient to produce the 2-thio-cyanomethylthiobenzothiazole.
Description
- 1 331 6~0 This invention relates to a process for the production of 2-thiocyanomethylthiobenzothiazole from 2-chloromethyl-thiobenzothiazole and an alkali metal thiocyanate or ammonium thiocyanate in the presence of a glycol ether solvent.
The compound 2-thi.ocyanomethylthiobenzothiazole (to be designated hereinafter as TCMTB) is a fully approved, registered, commercially available fungicide which is used as a preservative for tanned leather, for the prevention of mold growth on lumber and other surfaces, and as a microbicide in the pulp and paper and water treatment industries.
The first described synthesis of TCMTB was in U.S.
Patent Nos. 3,463,785 and 3,520,976, which patents also describe the composition and uses of the fungicide. In these patents, a method of preparation involved the reaction of chloromethylthiocyanate and sodium 2-mercaptobenzothiazole.
U.S. Patent No. 3,520,976 also disclosed the preparation of a 2-chloromethylthiobenzothiazole mixture from a metal salt of 2-mercaptobenzothiazole and a large excess of bromochloro-methane in the presence of acetone as solvent. The 2-chloro-methylthiobenzothiazole was then reacted with ammonium thio-cyanate using acetone as a solvent to produce a product containing 81.5% of TCMTB.
Japanese Patent Application No. 60-132971 describes the .
production of TCMTB by the reaction of a water-soluble salt of 2-mercaptobenzothiazole with chloromethylthiocyanate in the presence of water and a phase transfer catalyst. One disadvantage of any process which uses dhloromethylthio-~'~ .
- 1 - ,~ ~ ,,.
~ 33 1 620 cyanate is that this intermediate is not commerclally available. In addition, chloromethylthiocyanate is a powerful lachrymator and has a vile odor even at very low concentrations. Furthermore, it is a very toxic chemical with an acute oral LDso of 14.7 milligrams per kilogram of body weight in male and female rats.
U.S. Patent No. 3,669,981 describes the process for the production of 2-chloromethylthiobenzothiazole and contains a statement that this compound may be reacted with an alkali metal thiocyanate or ammonium thiocyanate in the presence of water and/or organic solvents to produce TCMTB.
U.S. Patent No. 4,755,609 discloses a process wherein 2-chloromethylthiobenzothiazole was reacted with an alkali metal thiocyanate or ammonium thiocyanate in aqueous solution at elevated temperatures of 70 to 100C in the presence of a phase transfer catalyst. There are several disadvantages in this process. This reaction must be run at relatively high temperatures in order to obtain good yields, but the aqueous medium can require extended reaction times and under these conditions TCMTB tends to decompose in water.
When the reaction is cooled for further processing, the TCMTB can separate as an oily layer. This layer will be contaminated by the presence of some dissolved alkali metal , I , . ~
chloride or ammonium chloride in water and also a portion of the phase transfer catalyst.
To obtain a pure product, it is necessary to dissolve the TCMTB layer in a water insoluble organic solvent and to then separate the organic layer from the aqueous contaminants. Alternatively, the TCMTB might be separated directly from the reaction mixture but, in this case, it will contain alkali metal chloride, water and phase transfer catalyst and some further processing will be required to purify the TCMTB.
If the technique of dissolving the TCMTB in a water insoluble organic solvent, such as methylene chloride, is used, the organic layer must be washed with water to remove the entrained alkali metal chloride, dried and distilled to remove the organic solvent.
If a low boiling organic solvent is used to facilitate distillation, problems of environmental pollution must be solved as the solvent is condensed and recycled. If a high boiling solvent is used, distillation will be more difficult and the TCMTB will be subject to temperatures that wi~l cause decomposition.
Recently, German Patent Publication DE 3,702,671 reported a procedure whereby liquid halomethylthiobenzo- -thiazole was reacted with an alkali metal thiocyanate or ammonium thiocyanate in the absence of a solvent and in the presence of a phase transfer catalyst, such as polyethylene glycol, polyethylene glycol monomethyl ether or polyethylene glycol dimethyl ether, at a temperature of 50 to 100C. When the reaction has been completed, an aromatic solvent is added. Glycol ether may also be added as a co-solvent. The mixture is filtered to remove the by-product alkali metal ..~
.
\
chloride or ammonium chloride as well as excess and unreacted thiocyanate salt.
The major disadvantage of this solvent-free reaction is that a phase transfer catalyst is required. These catalysts increase the cost of the process. In addition, when the aromatic hydrocarbon solvent is added and the mixture filtered, some of the catalyst will appear in the filtrate which is the desired product of the process.
The patent uses a substantial quantity of catalyst, up to 20~ of the 2-chloromethylthiobenzothiazole charge, and any carryover into the product has the possibility of causing compatibility problems. Regulatory agencies will also require additional toxicology tests if the catalyst has any toxic effects. In contrast, the process of the present invention will produce a product with a minimum amount of additional impurities present.
When the reaction of 2-chloromethylthiobenzothiazole and inorganic thiocyanate is run in an organic solvent, the solvent usually chosen is either acetone, methyl alcohol or ethyl alcohol because these are the organic solvents mentioned in the chemical literature as satisfactory for the reaction of inorganic thiocyanates and organic halides for the production of organic thiocyanates.
;
These solvents all have low boiling points, and the by- ~
product chloride salts are insoluble in the reaction mixture. -These chloride salts can be removed by filtration and the TCMTB product will then be obtained as a solution in the low .
boiling point solvent.
The low boiling point solvents which can be used to conduct the reaction are flammable and in some cases very toxic. Since severe restrictions are placed on the shipment of commercial products containing flammable solvents, it is always a disadvantage to market such a product if alternative processes can be discovered.
It has also been known to sell formulations of TCMTB
using glycol ethers as a sole or co-solvent. The formulation of TCMTB with glycol ether has, insofar as is known, always been subsequent to the manufacture of TCMTB.
It has been discovered that at least one glycol ether solvent can be used as a reaction solvent for the reaction of 2-chloromethylthiobenzothiazole with an alkali metal thio-cyanate or ammonium thiocyanate to produce solutions of TCMTBthat can be marketed without any elaborate purification procedures. We have found that glycol ethers are good solvents for the commonly used inorganic thiocyanates.
The reactions, moreover, can be run at moderate temperatures and high yields of the desired TCMTB can be obtained in a relatively short period of time.
The alkali metal chlorides and ammonium chloride produced as by-products are insoluble, depending on the temperature, in the reaction mixture and can be easily removed by filtration using commonly available commercial filters or by centrifugation using commercially available centrifuges. Furthermore, solutions of TCMTB that can be . . . ~ . . : ~- ; - - ~
formed in the process of the invention contain a sufficient quantity of TCMTB so that it is not necessary to concentrate or purify these solutions to obtain a marketable product.
It is, therefore, a principal object of the present invention to obviate the disadvantages of the prior art processes and provide an improved process for the preparation of TCMTB wherein at least one glycol ether is utilized as a reaction solvent.
It is another object of the invention to provide a unique process for the preparation of a glycol ether solution of TCMTB suitable for sale as a commercial product.
These and other objects and advantages will become apparent as the description proceeds.
SUM~A~Y OF THE INVENTION
This invention is a process for preparing 2-thiocyano-methylthiobenzothiazole comprising the step of reacting 2-chloromethylthiobenzothiazole with either an alkali metal thiocyanate or ammonium thiocyanate in the presence of at least one glycol ether as a solvent for the reaction, at a temperature, preferably 50 to 100C, and for a time sufficient to produce 2-thiocyanomethylthiobenzothiazole.
When the reaction procedure is completed, the product TCMTB
can be obtained as a concentrated solution in the glycol ether by separating the TCMTB solution from at least one insoluble by-product, such as an alkali metal chloride or ammonium chloride.
7 33 1 6~0 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The fungicide 2-thiocyanomethylthiobenzothiazole (TCMTB) is prepared in accordance with this invention by reacting 2-chloromethylthiobenzothiazole with an alkali metal thio-cyanate or ammonium thiocyanate in the presence of at leastone glycol ether as a solvent for the reaction.
The alkali metal is preferably sodium or potassium.
Sodium, potassium, and ammonium salts of thiocyanic acid are all soluble in glycol ethers.
The intermediate 2-chloromethylthiobenzothiazole may be prepared from sodium 2-mercaptobenzothiazole and bromochloro-methane as described in U.S. Patent No. 3,669,981.
The alkali metal thiocyanate and ammonium thiocyanate starting materials are commercially available or could be prepared by well-known methods by one of ordinary skill in the art.
Exemplary glycol ether solvents suitable in this invention include the monomethyl, monoethyl, monopropyl, monobutyl and monophenyl ethers of ethylene glycol and diethylene glycol; the monomethyl, monoethyl, monopropyl, monobutyl, and monophenyl ethers of propylene glycol, dipropylene glycol, and tripropylene glycol; and the dimethyl, diethyl, dipropyl and dibutyl ethers of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol. These solvents are either commercially available or obtainable by one of ordinary skill in the art by well-known methods.
133i62o The process of this invention is preferably conducted at a temperature of from about 50 to 100C. More preferably, the process is conducted at 60 to 80C, and most preferably at 60 to 70C.
The reactions are continued until the desired yield is obtained. A yield of more than 90~ can generally be readily attained using reaction times of about 3 to 7 hours. The reaction time will vary with the temperature used but long reaction times in excess of twelve hours should be avoided to minimize decomposition.
When the reaction is complete, the temperature can be reduced to below 30C at which temperature the by-product chloride salt will be present as a solid (insoluble) in the glycol ether - TCMTB. The solid salt can be removed by standard separation techniques, such as filtration or centrifugation. A filtrate or centrifugate may contain less than one percent of the chloride salt. The concentration of TCMTB contained in the final solution after separation will depend on the amount of solvent used.
The ratio of thiocyanate salt to 2-chloromethylthio-benzothiazole is preferably in the range of 0.8 to 1.2 moles of the thiocyanate salt per mole of 2-chloromethylthiobenzo-thiazole. Appreciable excess of thiocyanate salt will result in the salt being present as an impurity in the final product.
If desired, in one embodiment of the invention, the TCMTB produced by the process of the invention can be - .. : . .. ~ . .
' ? ~
obtained as an essentially solvent-free product from the glycol ether reaction mixture by removing both the insoluble by-product, such as the chloride salt, and the glycol ether f:rom the reaction mixture. The TCMTB will then be obtained al3 a viscous li~uid ranging in purity from 80 to ~0~.
However, the viscoùs liquid will crystallize under normal winter conditions in temperature climates. Since the product is normally shipped in 55 gallon drums or even larger containers it will then be necessary to warm the container to melt the contents if crystallization has occurred. This operation can lead to decomposition of the TCMTB if care is not used to control the warming operations.
For this reason, it is preferred to design the reaction procedure so that a concentrated solution of TCMTB is obtained in the glycol ether solvent. Concentrations in the range of 50 to 70~ by weight are preferred. These glycol ether solutions are particularly desirable because the high concentrations of TCMTB are stable even in cold weather. The solutions can then be readily formulated with surfactants, stabilizers, dyes, and other solvents to make emulsifiable products, dilute solutions or microemulsions.
The shelf stability of TCMTB solutions in either diethylene glycol monomethyl ether or diethylene glycol monoethyl ether solvent has been found to be excellent. Samples of 60~ TCMTB by ~r,;
1 :~31 G?n weight in these glycol ethers were evaluated over ten weeks time under four thermal conditions: 50C, 25C, 4C and -15C. No degradation was detected and onll minor crystal growth was observed in the -15C samples a week after seeding with pure crystalline TCMTB
The following examples illustrate the lnvention, but do not serve as limitations thereon.
EX~!~LE 1 A S00 mL, three-neck, round bottom flask equipped with a water-cooled condenser, mechanical stirrer, heating mantle and thermostatic control was charged with 1/2.4 g of technical grads 2-chloromethylthiobenzothiazole, ~4.8 g of sodium thiocyanate and 48 9 of diethylene glycol monomethyl ether. The mixture w~s agitatsd and he~ted to 70~C and held at that temperature for one hour. A fifteen aram sample was removed at that time. A five gram aliquot was cooled to room temperature, filtered through a 0.45 micson nylon membrane and the filtrate was analyzed for TCMTB using an HPLC method. The amount of TCMT~ in the diethylene glycol monomethyl ether solution represented a 78 percent yield.
The sampling prbcedure was repeated after threo hours reaction and the TCMTB yield was found to be 94 percent. At the end of five hours the reaction was cooled and the sampling procedure was repeated a third time. The final yield of TCMTB
was 98 percent.
--~0--. .:. :. : ::.~ .: :,; , : , :
o E~.AMPLE ~
The procedure described in Example 1 was repeated using seven other 915~col ether solvents at a temperature of 70C. The quantity of glycol ether solvent used amounted to 17~ of the total reaction mass. The percent yield of TCMTB was determined . after one, three, and five hours.
.~ .
Yiel~ of TCMTB (Percent) ~ne Three Five Sol~-ent Hour Hours Hours .~ !0 Diethvlene glycol monoethyl ether 86 96 100 Diethylene alyc-l monopropyl ether ,9 95 96 Ethylene alycol monophenyl ether 3, 80 94 Propylene glycol monomethyl ether 84 100 100 3 Dipropylene glycol monomethyl ether 73 90 94 Diethylene glycol ~imethyl ether 90 100 100 Diethylene glycol diethyl ether 70 100 100 .
~ . ' . ~1 . .
. . .
.... -- , .
"
.
..:
~ ',If~
I A 2L, three-neck, round-bottom flask equipped with a water-cooled condenser, mechanical stirrer, heating mantle and thermostatic control was charged with 647 g of technical grade 2-chloromethylthiobenzothiazole, 244 g of sodium thiocyanate and 195 g of diethylene glycol monomethyl ether.
The mixture was heated at 70C for five hours, cooled to 25C
' with a water bath and allowed to stand 30 minutes without agitation. The reaction mixture was transferred to a pressure filtration apparatus equipped with a 0.65 micron pore-size nylon membrane and filtered at 20 psig. The filtrate was weighed and analyzed and found to contain 76.3%
i~' of the TCMTB produced. The filter cake was then slurried with 195 g of diethylene glycol monomethyl ether at ambient temperature and passed through the filter again. This second filtrate was also weighed and analyzed and then combined with the original filtrate. The resulting solution contained 60 by weight of TCMTB and accounted for 92.1~ of the TCMTB
produced.
~h 20 The original filter cake was again reslurried with 195 g ~' of diethylene glycol monomethyl ether, filtered and analyzed.
The filtrate contained 6.9% of the TCMTB produced.
. Finally the filter cake was washed once more with ~; methylene chloride to determine the residual TCMTB in the :..:..
.` 25 cake. Only 1.0~ of the produced TCMTB was remaining in the cake.
i.`.`' ~:;''i ~ -12-`~
The compound 2-thi.ocyanomethylthiobenzothiazole (to be designated hereinafter as TCMTB) is a fully approved, registered, commercially available fungicide which is used as a preservative for tanned leather, for the prevention of mold growth on lumber and other surfaces, and as a microbicide in the pulp and paper and water treatment industries.
The first described synthesis of TCMTB was in U.S.
Patent Nos. 3,463,785 and 3,520,976, which patents also describe the composition and uses of the fungicide. In these patents, a method of preparation involved the reaction of chloromethylthiocyanate and sodium 2-mercaptobenzothiazole.
U.S. Patent No. 3,520,976 also disclosed the preparation of a 2-chloromethylthiobenzothiazole mixture from a metal salt of 2-mercaptobenzothiazole and a large excess of bromochloro-methane in the presence of acetone as solvent. The 2-chloro-methylthiobenzothiazole was then reacted with ammonium thio-cyanate using acetone as a solvent to produce a product containing 81.5% of TCMTB.
Japanese Patent Application No. 60-132971 describes the .
production of TCMTB by the reaction of a water-soluble salt of 2-mercaptobenzothiazole with chloromethylthiocyanate in the presence of water and a phase transfer catalyst. One disadvantage of any process which uses dhloromethylthio-~'~ .
- 1 - ,~ ~ ,,.
~ 33 1 620 cyanate is that this intermediate is not commerclally available. In addition, chloromethylthiocyanate is a powerful lachrymator and has a vile odor even at very low concentrations. Furthermore, it is a very toxic chemical with an acute oral LDso of 14.7 milligrams per kilogram of body weight in male and female rats.
U.S. Patent No. 3,669,981 describes the process for the production of 2-chloromethylthiobenzothiazole and contains a statement that this compound may be reacted with an alkali metal thiocyanate or ammonium thiocyanate in the presence of water and/or organic solvents to produce TCMTB.
U.S. Patent No. 4,755,609 discloses a process wherein 2-chloromethylthiobenzothiazole was reacted with an alkali metal thiocyanate or ammonium thiocyanate in aqueous solution at elevated temperatures of 70 to 100C in the presence of a phase transfer catalyst. There are several disadvantages in this process. This reaction must be run at relatively high temperatures in order to obtain good yields, but the aqueous medium can require extended reaction times and under these conditions TCMTB tends to decompose in water.
When the reaction is cooled for further processing, the TCMTB can separate as an oily layer. This layer will be contaminated by the presence of some dissolved alkali metal , I , . ~
chloride or ammonium chloride in water and also a portion of the phase transfer catalyst.
To obtain a pure product, it is necessary to dissolve the TCMTB layer in a water insoluble organic solvent and to then separate the organic layer from the aqueous contaminants. Alternatively, the TCMTB might be separated directly from the reaction mixture but, in this case, it will contain alkali metal chloride, water and phase transfer catalyst and some further processing will be required to purify the TCMTB.
If the technique of dissolving the TCMTB in a water insoluble organic solvent, such as methylene chloride, is used, the organic layer must be washed with water to remove the entrained alkali metal chloride, dried and distilled to remove the organic solvent.
If a low boiling organic solvent is used to facilitate distillation, problems of environmental pollution must be solved as the solvent is condensed and recycled. If a high boiling solvent is used, distillation will be more difficult and the TCMTB will be subject to temperatures that wi~l cause decomposition.
Recently, German Patent Publication DE 3,702,671 reported a procedure whereby liquid halomethylthiobenzo- -thiazole was reacted with an alkali metal thiocyanate or ammonium thiocyanate in the absence of a solvent and in the presence of a phase transfer catalyst, such as polyethylene glycol, polyethylene glycol monomethyl ether or polyethylene glycol dimethyl ether, at a temperature of 50 to 100C. When the reaction has been completed, an aromatic solvent is added. Glycol ether may also be added as a co-solvent. The mixture is filtered to remove the by-product alkali metal ..~
.
\
chloride or ammonium chloride as well as excess and unreacted thiocyanate salt.
The major disadvantage of this solvent-free reaction is that a phase transfer catalyst is required. These catalysts increase the cost of the process. In addition, when the aromatic hydrocarbon solvent is added and the mixture filtered, some of the catalyst will appear in the filtrate which is the desired product of the process.
The patent uses a substantial quantity of catalyst, up to 20~ of the 2-chloromethylthiobenzothiazole charge, and any carryover into the product has the possibility of causing compatibility problems. Regulatory agencies will also require additional toxicology tests if the catalyst has any toxic effects. In contrast, the process of the present invention will produce a product with a minimum amount of additional impurities present.
When the reaction of 2-chloromethylthiobenzothiazole and inorganic thiocyanate is run in an organic solvent, the solvent usually chosen is either acetone, methyl alcohol or ethyl alcohol because these are the organic solvents mentioned in the chemical literature as satisfactory for the reaction of inorganic thiocyanates and organic halides for the production of organic thiocyanates.
;
These solvents all have low boiling points, and the by- ~
product chloride salts are insoluble in the reaction mixture. -These chloride salts can be removed by filtration and the TCMTB product will then be obtained as a solution in the low .
boiling point solvent.
The low boiling point solvents which can be used to conduct the reaction are flammable and in some cases very toxic. Since severe restrictions are placed on the shipment of commercial products containing flammable solvents, it is always a disadvantage to market such a product if alternative processes can be discovered.
It has also been known to sell formulations of TCMTB
using glycol ethers as a sole or co-solvent. The formulation of TCMTB with glycol ether has, insofar as is known, always been subsequent to the manufacture of TCMTB.
It has been discovered that at least one glycol ether solvent can be used as a reaction solvent for the reaction of 2-chloromethylthiobenzothiazole with an alkali metal thio-cyanate or ammonium thiocyanate to produce solutions of TCMTBthat can be marketed without any elaborate purification procedures. We have found that glycol ethers are good solvents for the commonly used inorganic thiocyanates.
The reactions, moreover, can be run at moderate temperatures and high yields of the desired TCMTB can be obtained in a relatively short period of time.
The alkali metal chlorides and ammonium chloride produced as by-products are insoluble, depending on the temperature, in the reaction mixture and can be easily removed by filtration using commonly available commercial filters or by centrifugation using commercially available centrifuges. Furthermore, solutions of TCMTB that can be . . . ~ . . : ~- ; - - ~
formed in the process of the invention contain a sufficient quantity of TCMTB so that it is not necessary to concentrate or purify these solutions to obtain a marketable product.
It is, therefore, a principal object of the present invention to obviate the disadvantages of the prior art processes and provide an improved process for the preparation of TCMTB wherein at least one glycol ether is utilized as a reaction solvent.
It is another object of the invention to provide a unique process for the preparation of a glycol ether solution of TCMTB suitable for sale as a commercial product.
These and other objects and advantages will become apparent as the description proceeds.
SUM~A~Y OF THE INVENTION
This invention is a process for preparing 2-thiocyano-methylthiobenzothiazole comprising the step of reacting 2-chloromethylthiobenzothiazole with either an alkali metal thiocyanate or ammonium thiocyanate in the presence of at least one glycol ether as a solvent for the reaction, at a temperature, preferably 50 to 100C, and for a time sufficient to produce 2-thiocyanomethylthiobenzothiazole.
When the reaction procedure is completed, the product TCMTB
can be obtained as a concentrated solution in the glycol ether by separating the TCMTB solution from at least one insoluble by-product, such as an alkali metal chloride or ammonium chloride.
7 33 1 6~0 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The fungicide 2-thiocyanomethylthiobenzothiazole (TCMTB) is prepared in accordance with this invention by reacting 2-chloromethylthiobenzothiazole with an alkali metal thio-cyanate or ammonium thiocyanate in the presence of at leastone glycol ether as a solvent for the reaction.
The alkali metal is preferably sodium or potassium.
Sodium, potassium, and ammonium salts of thiocyanic acid are all soluble in glycol ethers.
The intermediate 2-chloromethylthiobenzothiazole may be prepared from sodium 2-mercaptobenzothiazole and bromochloro-methane as described in U.S. Patent No. 3,669,981.
The alkali metal thiocyanate and ammonium thiocyanate starting materials are commercially available or could be prepared by well-known methods by one of ordinary skill in the art.
Exemplary glycol ether solvents suitable in this invention include the monomethyl, monoethyl, monopropyl, monobutyl and monophenyl ethers of ethylene glycol and diethylene glycol; the monomethyl, monoethyl, monopropyl, monobutyl, and monophenyl ethers of propylene glycol, dipropylene glycol, and tripropylene glycol; and the dimethyl, diethyl, dipropyl and dibutyl ethers of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol. These solvents are either commercially available or obtainable by one of ordinary skill in the art by well-known methods.
133i62o The process of this invention is preferably conducted at a temperature of from about 50 to 100C. More preferably, the process is conducted at 60 to 80C, and most preferably at 60 to 70C.
The reactions are continued until the desired yield is obtained. A yield of more than 90~ can generally be readily attained using reaction times of about 3 to 7 hours. The reaction time will vary with the temperature used but long reaction times in excess of twelve hours should be avoided to minimize decomposition.
When the reaction is complete, the temperature can be reduced to below 30C at which temperature the by-product chloride salt will be present as a solid (insoluble) in the glycol ether - TCMTB. The solid salt can be removed by standard separation techniques, such as filtration or centrifugation. A filtrate or centrifugate may contain less than one percent of the chloride salt. The concentration of TCMTB contained in the final solution after separation will depend on the amount of solvent used.
The ratio of thiocyanate salt to 2-chloromethylthio-benzothiazole is preferably in the range of 0.8 to 1.2 moles of the thiocyanate salt per mole of 2-chloromethylthiobenzo-thiazole. Appreciable excess of thiocyanate salt will result in the salt being present as an impurity in the final product.
If desired, in one embodiment of the invention, the TCMTB produced by the process of the invention can be - .. : . .. ~ . .
' ? ~
obtained as an essentially solvent-free product from the glycol ether reaction mixture by removing both the insoluble by-product, such as the chloride salt, and the glycol ether f:rom the reaction mixture. The TCMTB will then be obtained al3 a viscous li~uid ranging in purity from 80 to ~0~.
However, the viscoùs liquid will crystallize under normal winter conditions in temperature climates. Since the product is normally shipped in 55 gallon drums or even larger containers it will then be necessary to warm the container to melt the contents if crystallization has occurred. This operation can lead to decomposition of the TCMTB if care is not used to control the warming operations.
For this reason, it is preferred to design the reaction procedure so that a concentrated solution of TCMTB is obtained in the glycol ether solvent. Concentrations in the range of 50 to 70~ by weight are preferred. These glycol ether solutions are particularly desirable because the high concentrations of TCMTB are stable even in cold weather. The solutions can then be readily formulated with surfactants, stabilizers, dyes, and other solvents to make emulsifiable products, dilute solutions or microemulsions.
The shelf stability of TCMTB solutions in either diethylene glycol monomethyl ether or diethylene glycol monoethyl ether solvent has been found to be excellent. Samples of 60~ TCMTB by ~r,;
1 :~31 G?n weight in these glycol ethers were evaluated over ten weeks time under four thermal conditions: 50C, 25C, 4C and -15C. No degradation was detected and onll minor crystal growth was observed in the -15C samples a week after seeding with pure crystalline TCMTB
The following examples illustrate the lnvention, but do not serve as limitations thereon.
EX~!~LE 1 A S00 mL, three-neck, round bottom flask equipped with a water-cooled condenser, mechanical stirrer, heating mantle and thermostatic control was charged with 1/2.4 g of technical grads 2-chloromethylthiobenzothiazole, ~4.8 g of sodium thiocyanate and 48 9 of diethylene glycol monomethyl ether. The mixture w~s agitatsd and he~ted to 70~C and held at that temperature for one hour. A fifteen aram sample was removed at that time. A five gram aliquot was cooled to room temperature, filtered through a 0.45 micson nylon membrane and the filtrate was analyzed for TCMTB using an HPLC method. The amount of TCMT~ in the diethylene glycol monomethyl ether solution represented a 78 percent yield.
The sampling prbcedure was repeated after threo hours reaction and the TCMTB yield was found to be 94 percent. At the end of five hours the reaction was cooled and the sampling procedure was repeated a third time. The final yield of TCMTB
was 98 percent.
--~0--. .:. :. : ::.~ .: :,; , : , :
o E~.AMPLE ~
The procedure described in Example 1 was repeated using seven other 915~col ether solvents at a temperature of 70C. The quantity of glycol ether solvent used amounted to 17~ of the total reaction mass. The percent yield of TCMTB was determined . after one, three, and five hours.
.~ .
Yiel~ of TCMTB (Percent) ~ne Three Five Sol~-ent Hour Hours Hours .~ !0 Diethvlene glycol monoethyl ether 86 96 100 Diethylene alyc-l monopropyl ether ,9 95 96 Ethylene alycol monophenyl ether 3, 80 94 Propylene glycol monomethyl ether 84 100 100 3 Dipropylene glycol monomethyl ether 73 90 94 Diethylene glycol ~imethyl ether 90 100 100 Diethylene glycol diethyl ether 70 100 100 .
~ . ' . ~1 . .
. . .
.... -- , .
"
.
..:
~ ',If~
I A 2L, three-neck, round-bottom flask equipped with a water-cooled condenser, mechanical stirrer, heating mantle and thermostatic control was charged with 647 g of technical grade 2-chloromethylthiobenzothiazole, 244 g of sodium thiocyanate and 195 g of diethylene glycol monomethyl ether.
The mixture was heated at 70C for five hours, cooled to 25C
' with a water bath and allowed to stand 30 minutes without agitation. The reaction mixture was transferred to a pressure filtration apparatus equipped with a 0.65 micron pore-size nylon membrane and filtered at 20 psig. The filtrate was weighed and analyzed and found to contain 76.3%
i~' of the TCMTB produced. The filter cake was then slurried with 195 g of diethylene glycol monomethyl ether at ambient temperature and passed through the filter again. This second filtrate was also weighed and analyzed and then combined with the original filtrate. The resulting solution contained 60 by weight of TCMTB and accounted for 92.1~ of the TCMTB
produced.
~h 20 The original filter cake was again reslurried with 195 g ~' of diethylene glycol monomethyl ether, filtered and analyzed.
The filtrate contained 6.9% of the TCMTB produced.
. Finally the filter cake was washed once more with ~; methylene chloride to determine the residual TCMTB in the :..:..
.` 25 cake. Only 1.0~ of the produced TCMTB was remaining in the cake.
i.`.`' ~:;''i ~ -12-`~
Claims (13)
1. A process for preparing 2-thiocyanomethylthiobenzo-thiazole consisting essentially of the steps of (a) reacting 2-chloromethylthiobenzothiazole with either alkali metal or ammonium thiocyanate in the presence of at least one glycol ether as a solvent for the thiocyanate, wherein the glycol ether is selected from the group consisting of the monomethyl, monoethyl, monopropyl, monobutyl and monophenyl ethers of ethylene glycol and diethylene glycol; the monomethyl, monoethyl, monopropyl, monobutyl, and monophenyl ethers of propylene glycol, dipropylene glycol, and tri-propylene glycol; and the dimethyl, diethyl, dipropyl and dibutyl ethers of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, at a temperature and for a time sufficient to produce said 2-thio-cyanomethylthiobenzothiazole in solution in the glycol ether and to produce at least one insoluble reaction by-product; and (b) separating said 2-thiocyanomethylthiobenzothiazole-glycol ether solution from said by-product to obtain a solution of 2-thiocyanomethylthiobenzothiazole in glycol ether.
2. A process as described in claim 1, wherein the solvent is diethylene glycol monomethyl ether.
3. A process as described in claim 1, wherein the solvent is diethylene glycol monoethyl ether.
4. A process as described in claim 1, wherein the solvent is propylene glycol monomethyl ether.
5. A process as described in claim 1, wherein the solvent is dipropylene glycol monomethyl ether.
6. A process as described in claim 1, wherein the solvent is diethylene glycol dimethyl ether.
7. A process as described in claim 1, wherein the solvent is diethylene glycol diethyl ether.
8. A process as described in claim 1, wherein the reaction temperature is maintained from 50 to 100°C.
9. A process as described in claim 8, wherein the reaction temperature is maintained from 60 to 70°C.
10. A process as described in claim 1, wherein said 2-thiocyanomethylthiobenzothiazole-glycol ether solution is separated from said by-product to obtain a solution of 2-thiocyanomethylthiobenzothiazole at concentration of 50 to 70 percent by weight in glycol ether.
11. A process as described in claim 1, wherein said process comprises the further steps of (a) reacting 2-chloromethylthiobenzothiazole with either alkali metal or ammonium thiocyanate in the presence of at least one glycol ether as a solvent for the thiocyanate, wherein the glycol ether is selected from the group consisting of the monomethyl, monoethyl, monopropyl, monobutyl and monophenyl ethers of ethylene glycol and diethylene glycol; the monomethyl, monoethyl, monopropyl, monobutyl, and monophenyl ethers of propylene glycol, dipropylene glycol, and tripropylene glycol; and the dimethyl, diethyl, dipropyl and dibutyl ethers of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, at a temperature and for a time sufficient to produce said 2-thio-cyanomethylthiobenzothiazole in solution in the glycol ether and to produce at least one insoluble reaction by-product;
(b) separating said 2-thiocyanomethylthiobenzothiazole-glycol ether solution from said by-product to obtain a solution of 2-thiocyanomethylthiobenzothiazole in glycol ether;
(c) washing said separated by-product with at least one glycol ether to obtain additional 2-thiocyanomethylthiobenzo-thiazole in glycol ether; and (d) combining said separated solution of 2-thiocyano-methylthiobenzothiazole in the glycol ether obtained in step (b) with said additional 2-thiocyanomethylthiobenzothiazole in glycol ether obtained by washing in step (c) to obtain a solution of 2-thiocyanomethylthiobenzothiazole at a concentration of from 40 to 65% by weight in glycol ether.
(b) separating said 2-thiocyanomethylthiobenzothiazole-glycol ether solution from said by-product to obtain a solution of 2-thiocyanomethylthiobenzothiazole in glycol ether;
(c) washing said separated by-product with at least one glycol ether to obtain additional 2-thiocyanomethylthiobenzo-thiazole in glycol ether; and (d) combining said separated solution of 2-thiocyano-methylthiobenzothiazole in the glycol ether obtained in step (b) with said additional 2-thiocyanomethylthiobenzothiazole in glycol ether obtained by washing in step (c) to obtain a solution of 2-thiocyanomethylthiobenzothiazole at a concentration of from 40 to 65% by weight in glycol ether.
12. A process as described in claim 1, wherein the alkali metal thiocyanate is sodium thiocyanate.
13. A process as described in claim 1, wherein the alkali metal thiocyanate is potassium thiocyanate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26847688A | 1988-11-04 | 1988-11-04 | |
| US268,476 | 1988-11-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1331620C true CA1331620C (en) | 1994-08-23 |
Family
ID=23023173
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000612630A Expired - Fee Related CA1331620C (en) | 1988-11-04 | 1989-09-22 | Process for the production of 2-thiocyanomethylthiobenzothiazole |
Country Status (14)
| Country | Link |
|---|---|
| EP (1) | EP0367635B1 (en) |
| JP (1) | JP2885431B2 (en) |
| AT (1) | ATE128126T1 (en) |
| AU (1) | AU621922B2 (en) |
| BR (1) | BR8905252A (en) |
| CA (1) | CA1331620C (en) |
| DE (1) | DE68924323T2 (en) |
| ES (1) | ES2080077T3 (en) |
| FI (1) | FI94244C (en) |
| GR (1) | GR3017880T3 (en) |
| MX (1) | MX170218B (en) |
| NO (1) | NO180335C (en) |
| NZ (1) | NZ230002A (en) |
| ZA (1) | ZA894986B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106922724A (en) * | 2017-03-06 | 2017-07-07 | 常州大学 | A kind of preparation of benzothiazole bactericidal liquid and its production method |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3520976A (en) * | 1968-12-24 | 1970-07-21 | Buckman Labor Inc | S-thiocyanomethyl compounds of 2-mercaptobenzothiazoles,2 - mercaptobenzoxazoles,and 2 - mercaptobenzimidazoles |
| BE754874A (en) * | 1969-10-30 | 1971-01-18 | Buckman Labor Inc | S-CHLOROMETHYLIC COMPOUNDS OF 2-MERCAPTO-BENZOTHIAZOLE, 2-MERCAPTOBENZOXAZOLE AND 2-MERCAPTOBENZIMIDAZOLE |
| DE3504966A1 (en) * | 1985-02-13 | 1986-08-14 | Bayer Ag, 5090 Leverkusen | METHOD FOR PRODUCING THIOCYANATOMETHYLTHIOBENZOTHIAZOLES |
| DE3702671C1 (en) * | 1987-01-30 | 1988-03-17 | Riedel De Haen Ag | Process for the preparation of thiocyanatomethylthiobenzothiazole |
-
1989
- 1989-06-30 ZA ZA894986A patent/ZA894986B/en unknown
- 1989-07-19 NZ NZ230002A patent/NZ230002A/en unknown
- 1989-08-22 JP JP1215887A patent/JP2885431B2/en not_active Expired - Lifetime
- 1989-09-01 FI FI894113A patent/FI94244C/en not_active IP Right Cessation
- 1989-09-15 AU AU41356/89A patent/AU621922B2/en not_active Ceased
- 1989-09-22 CA CA000612630A patent/CA1331620C/en not_active Expired - Fee Related
- 1989-10-12 BR BR898905252A patent/BR8905252A/en not_active IP Right Cessation
- 1989-11-03 MX MX1821889A patent/MX170218B/en unknown
- 1989-11-03 NO NO894382A patent/NO180335C/en unknown
- 1989-11-06 ES ES89311476T patent/ES2080077T3/en not_active Expired - Lifetime
- 1989-11-06 DE DE68924323T patent/DE68924323T2/en not_active Expired - Fee Related
- 1989-11-06 AT AT89311476T patent/ATE128126T1/en not_active IP Right Cessation
- 1989-11-06 EP EP89311476A patent/EP0367635B1/en not_active Expired - Lifetime
-
1995
- 1995-10-25 GR GR950402985T patent/GR3017880T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO894382D0 (en) | 1989-11-03 |
| ES2080077T3 (en) | 1996-02-01 |
| JPH02138180A (en) | 1990-05-28 |
| EP0367635A1 (en) | 1990-05-09 |
| MX170218B (en) | 1993-08-11 |
| NO894382L (en) | 1990-05-07 |
| ATE128126T1 (en) | 1995-10-15 |
| AU621922B2 (en) | 1992-03-26 |
| DE68924323D1 (en) | 1995-10-26 |
| GR3017880T3 (en) | 1996-01-31 |
| AU4135689A (en) | 1990-05-10 |
| NZ230002A (en) | 1991-01-29 |
| BR8905252A (en) | 1990-05-22 |
| NO180335C (en) | 1997-04-02 |
| ZA894986B (en) | 1990-07-25 |
| NO180335B (en) | 1996-12-23 |
| DE68924323T2 (en) | 1996-05-02 |
| EP0367635B1 (en) | 1995-09-20 |
| FI94244B (en) | 1995-04-28 |
| FI94244C (en) | 1995-08-10 |
| JP2885431B2 (en) | 1999-04-26 |
| FI894113A (en) | 1990-05-05 |
| FI894113A0 (en) | 1989-09-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5571941A (en) | Process for the purifying of iopamidol | |
| EP0377260A1 (en) | Method for the preparation of esters of beta-hydroxybutyric acid | |
| KR100200239B1 (en) | Process for preparing salts of clavulanic acid | |
| US5073638A (en) | Process for the production of 2-thiocyanomethylthiobenzothiazole | |
| CA1331620C (en) | Process for the production of 2-thiocyanomethylthiobenzothiazole | |
| US3993651A (en) | Triethylenediamine recovery | |
| EP0450684B1 (en) | A process for the preparation of D-(-)-4-hydroxyphenylglycine and L-(+)-4-hydroxyphenylglycine, starting from D.L.-4-hydroxyphenylglycine | |
| KR100352807B1 (en) | Production method of 5-acetoacetylamino-2-benzimidazolone | |
| US5571934A (en) | Process for preparing solutions of polyhydroxy-fatty acid amides having good color quality, and their use | |
| EP0154092B1 (en) | Process for the preparation of 2,4-dihydroxybenzophenones | |
| US4237066A (en) | Preparation of lower alkyl thiosemicarbazides | |
| EP0822184B1 (en) | Process for the preparation of N-substituted lactams | |
| EP1375491B1 (en) | Process for the preparation of 11(12)-pentadecen-15-olides | |
| US4263442A (en) | Process for the preparation of 2,3-dihydro-5,6-diphenyl-1,4-oxathiin | |
| US2917526A (en) | Process for the preparation of alkylmercuric-salts | |
| KR100427160B1 (en) | Method of reducing the amount of by-products in carbendazim by adding diazotization agents | |
| EP0090150A2 (en) | Process for preparing 4-hydroxy-2,5-dimethyl-2,3-dihydrofuran-3-one | |
| DE69613662T2 (en) | Process for the preparation of solutions of imidoalkanecarboxylic acids usable in peroxidation processes | |
| JPH07242633A (en) | Production of 5-aminoethylaminomethyl-2-chloropyridine | |
| CA1116608A (en) | Process for making selected 3-trihalomethyl-5-lower alkoxy-1,2,4-thiadiazoles | |
| KR20010021949A (en) | Method for Producing 3-Hydroxy-2-Methylbenzoic Acid | |
| GB1573517A (en) | 4-toluenesulphonic acid | |
| HU180743B (en) | Process for preparing triciolazole | |
| BE876376A (en) | PROCESS FOR PREPARING 2,2,6,6-TETRAMETHYL-4-OXOPIPERIDINE | |
| JPH0363554B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |